lib/oeqa/utils/oeqemuconsole.py: handle qemu serial console connection

lib/oeqa/utils/oeqemuconsole.py: handle qemu serial console connection

Python's telnetlib Telnet class connects only to AF_INET sockets, but we
want to use Unix domain socket for the qemu serial connection, so that's
why we override it.
Also we add a new read_all_timeout method similar to Telnet's read_all,
that read until a match or timeout and logs all output.

Signed-off-by: Stefan Stanacar <stefanx.stanacar@intel.com>